1. Field of the Invention
The present invention relates to a one-step dental adhesive composition with which a sustained release of fluorine can be effected. More particularly, a composition of the invention, when employed to make a bond between a dental restorative material such as a composite resin or a compomer and a substrate such as a biological hard tissue, especially an enamel or a dentin of a natural tooth as well as a glass ionomer cement, can be formed adhesive layer between them even in a convenient single step to give a firm adhesion, and, at the same time, exhibits an excellent sustained release of fluorine and an excellent material stability experience as a reduced water absorption, a reduced swelling and a reduced dimensional change. Accordingly, the present invention relates to a dental adhesive composition which can be handled conveniently by a one-step operation, exhibits an excellent durability, gives a high level of a sustained fluorine release, and thus is expected to give a secondary caries suppression.
2. Description of the Prior Art
In the field of a dentistry, an adhesive restoration method using a composite resin is brought into an increasing use in response to a recent advancement in a dental bonding technology. One such adhesive restoration method employed generally is a clinical procedure in which the surface of a tooth is treated with an etching agent containing an acid such as phosphoric acid and then subjected to an adhesive priming followed by a treatment with an adhesive composition containing a radical-polymerizable monomer having an acid group. However, this method involves a problematically complicated 3-step operation, and it gives an insufficient adhesion to a dentin although it gives a satisfactory adhesion to an enamel. More recently, a 2-step system employing a treatment with a so-called self etching primer and an adhesive composition was proposed. This method is brought into a clinical use increasingly due to its relatively easy handling and a high adhesiveness to a dentin. For example, JP 2634276 discloses a 2-step treatment in which a ground dentin is treated with a primer composition containing water, a polymerizable compound having a hydroxyl group, a polymerizable compound having an acid group and a curing agent and then with a photopolymerizable bonding agent whereby imparting an enamel and the dentin with a high adhesiveness. Nevertheless, a dental adhesive exerting a higher ability of binding to a substrate such as an enamel or a dentin more conveniently by an easier one-step procedure is still demanded strongly at a clinical stage of the dental surgery. Furthermore, a dental adhesive capable of providing not only a strong tooth adhesion but also a sustained release of fluorine which leads to inhibit the formation of a secondary caries is desired to be developed.
On the other hand, a glass ionomer (glass polyalkenoate) cement is considered increasingly to be of a clinical value since it exhibits a sustained release of fluorine and a satisfactory dental adhesion. Such glass ionomer cement undergoes a setting due to the formation of a hydrogel salt as a result of an acid-base reaction between a basic calcium aluminofluorosilicate glass and an acidic polymeric electrolite which is a homopolymer or a copolymer of an unsaturated carboxylic acid. A cement of this type is useful especially as a dental cement since it has an excellent biocompatibility and can adhere to a teeth where it can release a fluorine ion. However, it involves a problem relating to the material characteristics which are experienced as a slow setting between a glass and an ionomer as well as a brittleness of a hardened body whose matrix is in a gel structure.
Recently, a so-called photocuring glass ionomer cement was proposed. Mostly, it comprises a polyalkenoic acid, a reactive glass and a photopolymerizable monomer, and its photocuring allows the time period for achieving a desired hardness of the cement to be reduced when compared with a conventional glass ionomer cement, as described, for example, in JP-A-62-149715, JP-A-5-255033, JP-W-8-500080, JP-A-2-6358, JP-B-6-27047, JP-A-8-26925 and JP-A-8-30717. Nevertheless, none of these disclosed methods can achieve an actually strong adhesion to a substrate such as an enamel or a dentin.
JP-B-6-89050 discloses a setting composition (compomer) consisting of a vinyl monomer having an acid group, an ion-releasing filler and a polymerization initiator, especially a setting composition which requires no bonding agent for the adhesion, ensures a firm adhesion to a tooth even when being set as wet, and provides a hardened body having a sufficient hardness. However, since this composition exhibits an instability against water when used as a single pack, and also exhibits a poor storage stability, thus posing a problem when employed practically. When used as being divided into two components, a hardened article has problematically high water absorption and swelling. JP-A-10-236912 also discloses a adhesive composition comprising 100 parts by weight of a polymerizable unsaturated monomer containing 5% by weight or more of a polymerizable unsaturated monomer having an acid group, 2 to 30 parts by weight of a polyvalent metal ion-releasing filler, 3 to 30 parts by weight of water and 0.01 to 10 parts by weight of a polymerization initiator which is purported to be handled conveniently without requiring any pre-treatment and to give a strong adhesion to both of an enamel and a dentin but shows a reduced adhesion strength when the amount of water exceeds 30 parts by weight. However, this composition exhibits an extremely low sustained fluorine release from a cured adhesive, and has a problematically poor adhesive durability because of its high water absorption and swelling.
Accordingly, an objective of the present invention is to provide a dental adhesive composition which can adhere, by a convenient one-step operation, firmly to a biological hard tissue, especially an enamel or a dentin of a natural tooth as well as a glass ionomer cement, which exhibits an excellent sustained release of fluorine which may serve to inhibit the formation of a secondary caries, and which are excellent also in the material stability and in the adhesive durability due to its less oral water absorption and swelling.
Thus, the present invention relates to a dental adhesive composition comprising (A) 100 parts by weight of a polymerizable unsaturated monomer containing 5% by weight or more of a radical polymerizable monomer having an acid group, (B) 35 to 100 parts by weight of an acid-reactive filler, (C) 35 to 100 parts by weight of water, (D) 5 to 100 parts by weight of a water-soluble organic solvent; and (E) 0.1 to 10 parts by weight of a polymerization catalyst.
The present inventors made an effort to solve the problems described above which are associated with a dental adhesive and to obtain a dental adhesive capable of exerting a strong adhesion with a simple handling, and finally discovered that the adhesive composition of the present invention can adhere, by a convenient one-step operation, firmly to a substrate such as a biological hard tissue, especially an enamel or a dentin of a natural tooth, exhibits an excellent sustained release of fluorine which may serve to inhibit the formation of a secondary caries, and are excellent also in the material stability and in the adhesive durability due to its less oral water absorption or dimensional change, thus establishing the present invention.
In the invention, xe2x80x9ca dental adhesivexe2x80x9d means a material relating to an adhesive restoration employed clinically in a dental surgery, such as a dental bonding agent, a dental adhesive resin cement, a dental fissure sealant, a dental orthodontic bracket adhesive, a temporary sealing material (temporary sealing adhesive) and a root canal filling material and the like.